- Thesis
Authors: Goodwin, Nicole Cathleen (2006) - The first enantioselective, catalytic vinylogous Mukaiyama-Michael reaction of siloxyfurans with simple a,(3-unsaturated aldehydes has been reported using chiral imidazolidinones. This methodology provides access to enantioenriched y-butenolides, a privileged motif in organic synthesis. The utility of this organocatalytic Mukaiyama-Michael reaction was highlighted by the total syntheses of (-)-spiculisporic acid and (-)-5-epi-spiculisporic acid.
Investigations into the total syntheses of cylindrocyclophanes A and F necessitated
the development of a novel B-alkyl Suzuki cross-coupling of trimethylanilinium salts using
a nickel(O) catalyst and bulky phosphine ligand. This methodology study revealed a very
competitive nickel-catalyzed demethylation pathway, which produced dimethyla...
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- Thesis
Authors: Kurdyumov, Aleksey Valeryevich (2006) - For several years in our laboratory we have investigated the formal [3 + 3] cycloaddition. This is a condensation reaction that occurs between an unsaturated aldehyde and a 1,3-diketone or equivalent. The reaction results in a new 2H-pyran or 2H-pyridine fused to the diketone.
Chapter I of this thesis concentrates on new developments in the area of oxa-[3 + 3] cycloaddition reaction, in particular, Lewis acid catalyzed version of this reaction. Synthetic scope and limitations of this new methodology are discussed.
Chapter II describes synthetic approaches towards naturally occurring chromenes and chromanes. Our total syntheses of such compounds, rhododaurichromanic acid A and B, methyl ester of daurichromenic acid and hongoquercin A, are discussed in detail. Unusual, exo-type poly...
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- Thesis
Authors: Calad, Stacie Anne (2006) - Silylene transfer products can undergo stereoselective carbon-carbon bond-forming reactions, including the generation of quaternary carbon stereocenters, which demonstrate their utility in synthetic organic chemistry. Our laboratory has developed a metal-catalyzed method for di-tert-butylsilylene transfer to an alkene, providing silacyclopropane products. This dissertation describes the application of the metal-catalyzed silylene transfer conditions to carbonyl compounds. Metal-catalyzed silylene transfer to a range of a,13-unsaturated esters proved to be a general method for the formation of oxasilacyclopentene products containing a cyclic silyl ketene acetal functionality. These oxasilacyclopentenes are useful synthetic intermediates that can undergo facile and selective aldol add...
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- Thesis
Authors: Moore, Jennifer Anne (2006) - The recent surge of interest in Lanthanide (Ln) chemistry is focused on the synthesis and characterization of new families of mixed-valence Ln complexes for potential applications in electronics. Accessing mixed-valence systems in Ln chemistry has so far been difficult due to the lack of information available on these elements in an oxidation state other than the common Ln(III) state. We are interested in devising a series of complexes that feature two discrete Ln(II) metals ions and, via controlled intramolecular electron transfer, we aim to oxidize one of the Ln(II) species to a Ln(III), thus generating a mixed-valence complex. Although intramolecular electron transfer has been reported previously for a handful of Ln complexes, the transfer was spontaneous.
The reaction of the ...
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- Thesis
Authors: Nam, Tae-gyu (2006) - Pyridinol and pyrimidinol analogs of acetaminophen were synthesized as they have modified electronic properties without a significant structural modification. It was observed that inhibition of prostaglandin H2 synthases (PGHSs), or cyclooxygenases (COXs) by acetaminophen and the analogs is dependent on their abilities to donate a hydrogen atom or electron to the oxidized PGHS peroxidase heme. These abilities are reflected in their bond dissociation enthalpies (BDEs) and ionization potentials (IPs). Inhibitory activities of the analogs increased in the higher pH medium where the ionized form of the analogs are predominant, supporting that electron transfer from the analogs to peroxidase heme would be the major contributor to the mechanism of inhibition.
Pyridinol and pyrimidinol an...
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- Thesis
Authors: Tehan, Elizabeth Christine (2006) - Chemical sensors have become a valuable method for the detection and quantification of a multitude of analytes. The ideal sensor and sensor system would be portable, inexpensive, readily fabricated, and monitor and quantify several key analytes both simultaneously and reversibly.
The dissertation focuses on the development of new generation photonics-based chemical sensors and sensor systems by exploiting the benefits from sol-gel processing technology, pin printing methods, and low-power detection schemes. There are three main topics within this work. First, we describe techniques to provide a diverse sensor response to an analyte. Secondly, we describe the development of a compact sensor system. Lastly, we improve multianlayte sensing capabilities through advancements in material...
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- Thesis
Authors: Schultz, Mitchell John (2006) - The development of metal-catalysts for the oxidation of various functional groups is an ongoing endeavor in the field of organometallic chemistry. A constant challenge is employing practical oxidants, of which, molecular oxygen is advantageous because is it readily available, inexpensive, and produces benign byproducts. Herein, research performed by Mitchell John Schultz under the guidance of Professor Matthew S. Sigman on the Pd-catalyzed aerobic oxidation of alcohols and dialkoxylation of olefins is discussed.
Three Pd-catalysts developed for the aerobic oxidation of alcohols are presented and the effectiveness of each catalyst system is evaluated for a broad scope of alcohols. The application of these oxidation catalysts to chiral nonracemic, chemo-, and diastereoselective subst...
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- Thesis
Authors: Hong, Lian (2006) - Melanin is a pigment that is ubiquitous in the biological world. In addition to its obvious function of adornment, melanin is believed to serve as a metal reservoir and sunscreen. This work examined the metal binding behavior, the chemical structures and the interaction with light of natural melanins isolated from several different sources.
Sepia eumelanin was used as a model to study the metal binding behavior of eumelanins. Infrared spectroscopic analysis suggests that Mg(II), Ca(II) and Zn(II) are mainly bound to carboxyl groups and Cu(II) binds to hydroxyl groups at pH --4. The effect of metal content on the aerobic reactivity was examined by analyzing the ability of melanin to nick DNA. Of the metals studied, Cu(ll)- and Fe(III)-loaded melanin showed the most damaging effects ...
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Authors: Kim, Seong-cheol (2006) - New synthetic methods for the polymerization were investigated via biocatalysis. Horseradish peroxidase (HRP) was used to synthesize the functionalized polyanilines. The biocatalytic route has significant importance because the chemical and electrochemical methods sometimes do not allow the monomers polymerized.
In the second chapter, the enzymatic synthesis of the aniline which has a carboxylic acid (CA) group was investigated with polycationic templates at moderately acidic pH (pH 4-- 6). The optimum pH conditions of polymerization were higher than the pKa value of an amine and that of carboxylic acid. One positive charge in a template, could on average, template up to three monomers.
In the third chapter, the unusual doping behavior of PCA/template complex at pH 13 was discusse...
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- Thesis
Authors: Wang, Chih Hung (2006) - This dissertation describes efforts towards the assembling of structurally diversified heterocycles using radical chemistry. Reaction mechanisms for the formation of these novel compounds and their structural analysis are also presented. Furthermore, we describe the success we have achieved in eantioselective syntheses that transfer chirality from the radical precursor to the newly formed stereocenter(s) in the products during radical reactions. The novel compounds that have been prepared could possibly serve as pharmacophores in drug discovery projects.
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